Illumination optical system and projection display optical system

ABSTRACT

An illumination optical system which can use light from a light source with high efficiency and can provide an illumination luminous flux with highly uniform illuminance, is disclosed. The illumination optical system illuminates an illumination surface with a generally telecentric illumination luminous flux. In light intensity distribution of illumination light on the illumination surface changing depending on a deviation angle of an incident ray with respect to a normal to the illumination surface, the illumination optical system operates the illumination luminous flux such that a ratio of angle widths at which light intensity reaches half of a peak value in each of two axis directions orthogonal to each other on the illumination surface is an aspect ratio of 2:1.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an illumination optical systemand a projection display optical system which are used in a projectiontype image display apparatus.

[0003] 2. Description of Related Art

[0004] Conventionally, in a projector type display (a projection typeimage display apparatus), a liquid crystal display panel or amicromirror array device panel is typically used as a light modulationelement for switching to control transmission and shielding ordeflection of light to project a selected light pattern onto a screen,thereby displaying an image on the screen.

[0005] In the projector which employs the liquid crystal display panelor the micromirror array device panel as the light modulation element,it is important to use light from a light source with high efficiencyand reduce variations in illuminance on the screen.

[0006] An optical integrator formed of two lens arrays each includinglenses arranged two-dimensionally is a known means for improvement. Inthe optical integrator, a first lens array splits a luminous flux from alight source into a plurality of luminous fluxes, and a second lensarray enlarges the luminous fluxes and forms images by the luminousfluxes superimposed one on another on a display area of a lightmodulation element (see Japanese Patent Application Laid-Open No.11(1999)-64848).

[0007] In this method, since the split luminous fluxes with smallvariations in illuminance are superimposed, the resulting irradiationlight has high uniformity to significantly reduce variations inilluminance on the screen. When the first lens array has each apertureformed in a rectangular shape similar to the display area of the lightmodulation element, all the split luminous fluxes are irradiated to thedisplay area without waste. This improves the efficiency of theirradiation light and thus improves the use efficiency of the light fromthe light source.

[0008] Another means for improvement is to guide light from a lightsource to a kaleidoscope to mix the vectors of light rays to provideuniform light intensity distribution at an end surface of thekaleidoscope from which the light emerges, and then form a conjugateimage by an image-forming lens on a micromirror array device used as alight modulation element.

[0009] When the kaleidoscope is used, an optical system is complicatedif a means for converting natural emission light from the light sourceinto linearly polarized light is used. Thus, such a means is not usedgenerally.

[0010] In the method, the resulting irradiation light has highuniformity to significantly reduce variations in illuminance on ascreen.

[0011] However, in the method of providing uniform light intensitydistribution using the optical integrator formed of two lens arrays orthe kaleidoscope, the luminous flux illuminating the light modulationelement has a large convergent angle. When the light modulation panel isrealized by a reflection type liquid crystal display panel or amicromirror array device, limitations are imposed on space for formingan optical path along which the illumination light is guided. When a TIRprism is used to guide light, the minimum angle of total reflection islimited. When a polarization beam splitter is used to guide light,limitations are imposed due to dependency of the reflectivity of S waveson the incident angle. From these facts, the illumination luminous fluxincident on the light modulation element is desirably close to acollimated luminous flux.

[0012] In addition, when a transmission type liquid crystal displaypanel is used as the light modulation element to modulate light of treeprimary colors of red, green, and blue, the modulated light componentsare then combined by a dichroic mirror or dichroic prism. In this case,as the modulated light is less similar to a collimated luminous flux,the cut wavelength in a reflection/transmission wavelength region of adichroic film is changed to produce turbidity of colors or variations incolor reproducibility depending on the position of a projected image.

[0013] When twisted nematic liquid crystal (TNLC) is used as the lightmodulation element, whether it is of a transmission type or a reflectiontype, as the incident angle of an illumination luminous flux on theliquid crystal display panel is more inclined with respect to the normalto the panel, and more inclined with respect to the rubbing direction ofliquid crystal molecules in the liquid crystal display panel plane, alarger deviation occurs from 0 or π which is an ideal phase differenceof a wave provided by transmission through the liquid crystal displaypanel. Therefore, contrast in light modulation is reduced.

SUMMARY OF THE INVENTION

[0014] It is an object of the present invention to provide anillumination optical system which can use light from a light source withhigh efficiency and can provide an illumination luminous flux withhighly uniform illuminance, and a projection display optical system anda projection type image display apparatus which can achieve a projectedimage with a higher brightness and a higher contrast.

[0015] To achieve the aforementioned objects, according to one aspect,the present invention provides an illumination optical system whichilluminates an illumination surface with a generally telecentricillumination luminous flux (which means that it includes somewhatdivergent and convergent components), wherein the illumination opticalsystem optically operates the illumination luminous flux such that, inintensity distribution of illumination light on the illumination surfacechanging depending on a deviation angle of an incident ray with respectto the normal to the illumination surface, a ratio of angle widths atwhich light intensity reaches half of a peak value in each of two axisdirections orthogonal to each other on the illumination surface is anaspect ratio of 2:1 or higher.

[0016] According to second aspect, the present invention provides anillumination optical system which optically operates an illuminationluminous flux incident as a generally collimated luminous flux (whichmeans that it includes somewhat divergent and convergent components),comprising an optical integrator and a light intensity conversionelement. The optical integrator performs splitting and recombination ona luminous flux in a first axis direction on a section generallyorthogonal to the traveling direction of the illumination luminous flux.The light intensity conversion element performs conversion of lightintensity distribution of the illumination luminous flux in a secondaxis direction orthogonal to the first axis direction on the section.

[0017] According to third aspect, the present invention provides aprojection display optical system comprising the illumination opticalsystem, a spatial light modulation element which modulates a luminousflux emerging from the illumination optical system by a group of pixelsarranged two-dimensionally, and a projection lens which projects theluminous flux modulated by the spatial light modulation element onto aprojection surface.

[0018] These and other characteristics of the present invention will beapparent from the following description of specific embodiments withreference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 schematically shows the structure of an illuminationoptical system which is Embodiment 1 of the present invention;

[0020]FIG. 2 schematically shows the structure of an illuminationoptical system which is Embodiment 2 of the present invention;

[0021]FIG. 3 is a schematic diagram for explaining the function of anoptical integrator incorporated in the illumination optical systems ofEmbodiments 1 and 2;

[0022]FIG. 4 is a schematic diagram for explaining the function of lightintensity conversion optics incorporated in the illumination opticalsystem of Embodiment 1;

[0023]FIG. 5 is a schematic diagram for explaining the function of lightintensity conversion optics incorporated in the illumination opticalsystem of Embodiment 2;

[0024] FIGS. 6(A) to 6(C) are diagrams for explaining the process ofproducing generally uniform light intensity distribution by theillumination optical system of Embodiment 1;

[0025] FIGS. 7(A) to 7(C) are graphs for explaining the process ofproducing generally uniform light intensity distribution by theillumination optical system of Embodiment 1;

[0026]FIG. 8(A) to 6(C) are diagrams for explaining the process ofproducing generally uniform light intensity distribution by theillumination optical system of Embodiment 2;

[0027] FIGS. 9(A) to 9(C) are graphs for explaining the process ofproducing generally uniform light intensity distribution by theillumination optical system of Embodiment 2;

[0028] FIGS. 10(A) to 10(C) show light irradiation angle distribution ona light modulation panel by the illumination optical system ofEmbodiments 1 and 2;

[0029] FIGS. 11(A) to 10(C) show light irradiation angle distribution ona light modulation panel by an illumination optical system using aconventional two-dimensional optical integrator;

[0030]FIG. 12 is a schematic diagram showing the structure of aprojection type image display apparatus which is Embodiment 3;

[0031]FIG. 13 is a schematic diagram showing the structure of aprojection type image display apparatus which is Embodiment 4;

[0032]FIG. 14 is a schematic diagram showing the structure of aprojection type image display apparatus which is Embodiment 5; and

[0033]FIG. 15 is a schematic diagram showing the structure of aprojection type image display apparatus which is Embodiment 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

[0034]FIG. 1 shows the structure of an illumination optical system whichis Embodiment 1 of the present invention. In FIG. 1, reference numeral100 shows a gas exciting light emission source serving as a lightsource. As the light source 100, a high-pressure mercury lamp, a metalhalide lamp, a xenon lamp or the like is used.

[0035] The light source 100 is used in combination with a parabolicreflecting mirror 101 to produce a generally collimated visible lightbeam. To provide a high-quality collimated luminous flux with thesmallest possible divergence (the smallest possible divergence angle), aminimized discharge gap is designed to limit an electron excited area ina gas, and the light source 100 emits light close to that emitted by apoint source of light.

[0036] To make the light emission source closer to a point source,instead of applying an AC bias to the discharge gap to emit electronsfrom both directions of electrodes to form two point sources of light, aDC bias may be applied to produce a point source of light with highluminance on the side of a cathode while the efficiency of lightemission and the efficiency of energy conversion are reduced.

[0037] Of the luminous flux emitted from a lamp unit formed of the gasexciting light source 100 and the parabolic reflecting mirror 101,ultraviolet rays outside visible light are cut by an ultraviolet ray cutfilter 102. The ultraviolet rays excite or degrade optical glass used asa material of a lens or an optical thin film in the long term. However,a major purpose of the ultraviolet ray cut filter 102 is to prevent theultraviolet rays from decomposing and altering a liquid crystal polymerwhich is an organic material when a liquid crystal element is used for alight modulation panel.

[0038] The luminous flux of visible light transmitted through theultraviolet ray cut filter 102 is then incident on a shuffling prism 103and a reflecting mirror 104 which serve as light intensity conversionelements disposed in a predetermined area of the luminous flux, anddeflected and reflected. The shuffling prism 103 used in this case has ashape provided by folding an opposite apical angle prism on a reflectingsurface of the reflecting mirror 104. The effects of the shuffling prism103 are later described with reference to FIG. 4.

[0039] Then, the luminous flux transmitted through the shuffling prism103 and reflected by the reflecting mirror 104 is incident on a firstcylindrical lens 105. The first cylindrical lens 105 has a refractivepower only in a horizontal direction in FIG. 1, and forms a beamcompressor as a pair with a second cylindrical lens 110 disposed in adirection in which the luminous flux travels.

[0040] Thus, the luminous flux incident on the first cylindrical lens105 is compressed in the horizontal direction in FIG. 1, and is guidedto a light modulation panel 112 in the afocal state.

[0041] The luminous flux transmitted through the first cylindrical lens105 is incident on a first cylindrical array homogenizer 106. The firstcylindrical array homogenizer 106 is formed of an array of lenses havinga refractive power only in a vertical direction in FIG. 1. The firstcylindrical array homogenizer 106 splits the incident luminous flux intoa plurality of luminous fluxes, the number of which is equal to thenumber of the lenses of the array, and focal lines are individuallyformed, and then a cylindrical condenser lens 109 converts the luminousfluxes into collimated luminous fluxes set to have a predeterminedwidth.

[0042] The spacing between the principal planes of the first cylindricalarray homogenizer 106 and the cylindrical condenser lens 109 is set tothe sum of the focal length of the first cylindrical array homogenizer106 and the focal length of the cylindrical condenser lens 109. Thiscauses the luminous fluxes to be converted into collimated luminousfluxes as described above.

[0043] Since the first cylindrical array homogenizer 106 has an opticalaxis line decentered with respect to an optical axis line of each lensof the array, the cylindrical condenser lens 109 superimposes theluminous fluxes transmitted through the respective lenses of the arrayof the first cylindrical array homogenizer 106 at the position of afocal line of the cylindrical condenser lens 109. This achieves anoptical integration (split and recombination of the luminous fluxes)operation.

[0044] The position of the focal line of the cylindrical condenser lens109 corresponds to a modulation surface of the light modulation panel(spatial light modulation element) 112.

[0045] The positions of focal lines of a second cylindrical arrayhomogenizer 107 are set to the positions of pupils of the respectivelenses of the array of the first cylindrical array homogenizer 106. Thetandem lens structure of the second cylindrical array homogenizer 107and the cylindrical condenser lens 109 results in an optically conjugaterelationship between the pupils of the respective lenses of the array ofthe first cylindrical array homogenizer 106 and the modulation surfaceof the light modulation panel 112. Consequently, the pupils of therespective lenses of the array of the first cylindrical arrayhomogenizer 106 are imaged on the modulation surface of the lightmodulation panel 112 in the vertical direction in FIG. 1.

[0046] The luminous flux emitted from the lamp unit formed of the gasexciting light source 100 and the parabolic reflecting mirror 101 is notcompletely collimated and has slight divergence. The second cylindricalarray homogenizer 107 corrects the divergence of the luminous flux toreliably guide the luminous flux transmitted through the pupil of eachlens of the array of the first cylindrical array homogenizer 106 to themodulation surface of the light modulation panel 112.

[0047] The luminous fluxes transmitted through the second cylindricalarray homogenizer 107 are incident on a polarization conversion elementarray 108. The polarization conversion element array 108 used in thiscase is similar to that called a PS conversion element which isgenerally used in a liquid crystal projector. The polarizationconversion element 108 changes the light emitted from the lamp unit intopolarized light components in parallel with one direction, for examplewith the vertical direction in FIG. 1, by an array of polarization beamsplitters.

[0048] Specifically, the polarization conversion element array 108transmits light components polarized in the vertical direction in FIG. 1through a polarization splitting film (not shown) and reflects lightcomponents polarized in the horizontal direction in FIG. 1 by thepolarization splitting film, and the reflected light components areagain reflected by a polarization splitting film of the adjacentpolarization beam splitter of the array to shift the optical path by apitch in the array. The polarization direction of the light is changed90 degrees by a half-wave plate (not shown) immediately before emergingfrom the polarization light conversion element array 108, and then thelight emerges as linearly polarized light in the vertical direction inFIG. 1. In this manner, all luminous fluxes transmitted through thepolarization conversion element array 108 become linearly polarizedlight in the vertical direction in FIG. 1.

[0049] The luminous fluxes transmitted through the polarizationconversion element array 108 are incident on the cylindrical condenserlens 109, and superimposed with each other in the vertical direction inFIG. 1 for integration on the modulation surface of the light modulationpanel 112 located at the position of the focal line of the cylindricalcondenser lens 109.

[0050] The luminous fluxes transmitted through the cylindrical condenserlens 109 are incident on the second cylindrical lens 110. Thecylindrical lens 110 has a refractive power only in the horizontaldirection in FIG. 1 and forms the beam compressor as a pair with thefirst cylindrical lens 105 as described above. Thus, the luminous fluxesare compressed in the horizontal direction in FIG. 1 and guided to thelight modulation panel 112 in the afocal state.

[0051] The second cylindrical lens 110 is arranged to dispose a pupil ofthe first cylindrical lens 105 and the modulation surface of the lightmodulation panel 112 in an optically conjugate relationship. The pupilof the first cylindrical lens 105 is imaged on the modulation surface ofthe light modulation panel 112 in the horizontal direction in FIG. 1.

[0052] The second cylindrical lens 110 is provided for correcting thedivergence of the luminous flux emitted from the lamp unit formed of thegas exciting light source 100 and the parabolic reflecting mirror 101 toreliably guide the luminous flux transmitted through the pupil of thefirst cylindrical lens 105 to the modulation surface of the lightmodulation panel 112, similarly to the cylindrical array homogenizer 107described above.

[0053] The luminous fluxes transmitted through the cylindrical lens 110are incident on a dummy polarization beam splitter 111. The dummy may beformed of a dichroic prism or mirror instead. Whether the dummy isformed of a polarization beam splitter or a dichroic prism, thedeflection direction of the luminous fluxes is set to the horizontaldirection in FIG. 1.

[0054] As described above, the luminous fluxes transmitted through theillumination optical system of Embodiment 1 are guided to the lightmodulation panel 112. The illumination characteristics of Embodiment 1are later described.

Embodiment 2

[0055]FIG. 2 shows the structure of an illumination optical system whichis Embodiment 2 of the present invention. In FIG. 2, reference numeral200 shows a gas exciting light emission source serving as a lightsource. As the light source 200,a high-pressure mercury lamp, a metalhalide lamp, a xenon lamp or the like is used. The light source 200 isused in combination with a parabolic reflecting mirror 201 to produce agenerally collimated visible light beam. To provide a high-qualitycollimated luminous flux with the smallest possible divergence (thesmallest possible divergence angle), the light source 200 is designed tohave a minimized discharge gap to limit an electron excited area in agas, and the light source 200 emits light close to that emitted by apoint source of light.

[0056] To make the light emission source closer to a point source oflight, instead of applying an AC bias to the discharge gap to emitelectrons from both directions of electrodes to form two point sourcesof light, a DC bias may be applied to produce a point source of lightwith high luminance on the side of a cathode while the efficiency oflight emission and the efficiency of energy conversion are reduced.

[0057] Of the luminous flux emitted from a lamp unit formed of the gasexciting light source 200 and the parabolic reflecting mirror 201,ultraviolet rays outside visible light are cut by an ultraviolet ray cutfilter 202. The ultraviolet rays excite or degrade optical glass used asa material of a lens or an optical thin film in the long term. However,a major purpose of the ultraviolet ray cut filter 202 is to prevent theultraviolet rays from decomposing and altering a liquid crystal polymerwhich is an organic material when a liquid crystal element is used for alight modulation panel.

[0058] Next, the luminous flux of visible light transmitted through theultraviolet ray cut filter 202 is incident on a first cylindrical arrayhomogenizer 206. The first cylindrical array homogenizer 206 has arefractive power only in a vertical direction in FIG. 1. The firstcylindrical array homogenizer 206 splits the incident luminous flux intoa plurality of luminous fluxes, the number of which is equal to thenumber of lenses of the array, and focal lines are individually formed,and then a cylindrical condenser lens 209 converts the luminous fluxesinto collimated luminous fluxes set to have a predetermined width.

[0059] The spacing between the principal planes of the first cylindricalarray homogenizer 206 and the cylindrical condenser lens 209 is set tothe sum of the focal length of the first cylindrical array homogenizer206 and the focal length of the cylindrical condenser lens 209. Thiscauses the luminous fluxes to be converted into collimated luminousfluxes as described above.

[0060] Since the first cylindrical array homogenizer 206 has an opticalaxis line decentered with respect to an optical axis line of each lensof the array, the cylindrical condenser lens 209 superimposes theluminous fluxes transmitted through the respective lenses of the arrayof the first cylindrical array homogenizer 206 at the position of afocal line of the cylindrical condenser lens 209. This achieves anoptical integration operation. The position of the focal line of thecylindrical condenser lens 209 corresponds to a modulation surface of alight modulation panel 212.

[0061] The luminous fluxes transmitted through the first cylindricalarray homogenizer 206 are transmitted through a second cylindrical arrayhomogenizer 207. The positions of focal lines of the second cylindricalarray homogenizer 207 are set to the positions of pupils of therespective lenses of the array of the first cylindrical arrayhomogenizer 206. The tandem lens structure of the second cylindricalarray homogenizer 207 and the cylindrical condenser lens 209 results inan optically conjugate relationship between the pupils of the respectivelenses of the array of the first cylindrical array homogenizer 206 andthe modulation surface of the light modulation panel 212. Consequently,the pupils of the respective lenses of the array of the firstcylindrical array homogenizer 206 are imaged on the modulation surfaceof the light modulation panel 212 in the vertical direction in FIG. 2.

[0062] The luminous flux emitted from the lamp unit formed of the gasexciting light source 200 and the parabolic reflecting mirror 201 is notcompletely collimated and has slight divergence. The second cylindricalarray homogenizer 207 corrects the divergence of the luminous flux toreliably guide the luminous flux transmitted through the pupil of eachlens of the array of the first cylindrical array homogenizer 206 to themodulation surface of the light modulation panel 212.

[0063] The luminous fluxes transmitted through the second cylindricalarray homogenizer 207 are incident on a polarization conversion elementarray 208. The polarization conversion element array 208 is similar tothat called a PS conversion element which is generally used in a liquidcrystal projector. The polarization conversion element array 208 changesthe light emitted from the lamp unit into polarized light components inparallel with one direction, for example with the vertical direction inFIG. 2, by an array of polarization beam splitters. Specifically, thepolarization conversion element array 208 transmits light componentspolarized in the vertical direction in FIG. 2 through a polarizationsplitting film and reflects light components polarized in the horizontaldirection in FIG. 2 by the polarization splitting film, and thereflected light components are again reflected by a polarizationsplitting film of the adjacent polarization beam splitter of the arrayto shift the optical path by a pitch in the array. The polarizationdirection of the light is changed 90 degrees by a half-wave plate (notshown) immediately before emerging from the polarization lightconversion element array, and then the light emerges as linearlypolarized light in the vertical direction in FIG. 2. In this manner, allluminous fluxes transmitted through the polarization conversion elementarray 208 become linearly polarized light in the vertical direction inFIG. 2.

[0064] The luminous fluxes transmitted through the polarizationconversion element array 208 are incident on a first cylindrical lens205. The first cylindrical lens 205 has a refractive power only in ahorizontal direction in FIG. 2, and forms a beam compressor as a pairwith a second cylindrical lens 210 disposed in a direction in which theluminous fluxes travel. Thus, the luminous fluxes incident on the firstcylindrical lens 205 are compressed in the horizontal direction in FIG.2, and are basically guided to the light modulation panel 212 in theafocal state.

[0065] In Embodiment 2, however, the beam compressor is intentionallyprovided with a predetermined amount of pupil distortion aberrationwhich controls light intensity on the modulation surface of the lightmodulation panel 212 to have uniform or arbitrary distribution. Theeffects of the pupil distortion aberration of the beam compressor arelater described with reference to FIG. 5.

[0066] The luminous fluxes transmitted through the first cylindricallens 205 are incident on the cylindrical condenser lens 209. Asdescribed above, the cylindrical condenser lens 209 superimposes theluminous fluxes in the vertical direction in FIG. 2 for integration onthe modulation surface of the light modulation panel 212 located at theposition of the focal line of the cylindrical condenser lens 209.

[0067] The luminous fluxes transmitted through the cylindrical condenserlens 209 are incident on the second cylindrical lens 210. The secondcylindrical lens 210 has a refractive power only in the horizontaldirection in FIG. 2 and forms the beam compressor as a pair with thefirst cylindrical lens 205 as described above. Thus, the luminous fluxesare compressed in the horizontal direction in FIG. 2 and guided to thelight modulation panel 212 in the afocal state.

[0068] The second cylindrical lens 210 is arranged to dispose a pupil ofthe first cylindrical lens 205 and the modulation surface of the lightmodulation panel 212 in an optically conjugate relationship (theoptically conjugate relationship has low accuracy due to the aberrationintentionally provided for the beam compressor). The pupil of the firstcylindrical lens 205 is thus imaged on the modulation surface of thelight modulation panel 212 in the horizontal direction in FIG. 2.

[0069] The second cylindrical lens 210 is provided for correcting thedivergence of the luminous flux emitted from the lamp unit formed of thegas exciting light source 200 and the parabolic reflecting mirror 201 toreliably guide the luminous flux transmitted through the pupil of thefirst cylindrical lens 205 to the modulation surface of the lightmodulation panel 212, similarly to the function of the secondcylindrical array homogenizer 207.

[0070] The luminous fluxes transmitted through the cylindrical lens 210are incident on a dummy polarization beam splitter 211. The dummy may beformed of a dichroic prism or mirror instead. Whether the dummy isformed of a polarization beam splitter or a dichroic prism, thedeflection direction of the luminous fluxes is set to the horizontaldirection in FIG. 2.

[0071] As described above, the luminous fluxes transmitted through theillumination optical system of Embodiment 2 are guided to the lightmodulation panel 212. The illumination characteristics of Embodiment 2are later described.

[0072] (About Optical Integrator)

[0073] Next, description is made for the optical integrators used in theillumination optical systems of Embodiments 1 and 2 with reference toFIG. 3.

[0074] In optical elements disposed in FIG. 3, a first cylindrical arrayhomogenizer 306 corresponds to the first cylindrical array homogenizer106 in Embodiment 1 and corresponds to the first cylindrical arrayhomogenizer 206 in Embodiment 2. A second cylindrical array homogenizer307 corresponds to the second cylindrical array homogenizer 107 inEmbodiment 1 and corresponds to the second cylindrical array homogenizer207 in Embodiment 2.

[0075] A cylindrical condenser lens 309 corresponds to the cylindricalcondenser lens 109 in Embodiment 1 and corresponds to the cylindricalcondenser lens 209 in Embodiment 2.

[0076] The first and second cylindrical array homogenizers 306 and 307and the cylindrical condenser lens 309 constitute the opticalintegrator.

[0077] A light modulation panel 312 in FIG. 3 corresponds to the lightmodulation panel 112 in Embodiment 1 and corresponds to the lightmodulation panel 212 in Embodiment 2.

[0078] A luminous fluxes indicated by an arrow in FIG. 3, which isguided to the first cylindrical array homogenizer 306, and generallycollimated in an optical integration direction is split by pupils oflenses in the array in the vertical direction in FIG. 3 and condensed onrespective focal lines. The positions of the focal lines of the firstcylindrical array homogenizer 306 are close to the positions of pupilsof the second cylindrical array homogenizer 307, and are arranged suchthat the incident luminous flux indicated by the arrow is hardlysubjected to a refractive effect by the second cylindrical arrayhomogenizer 307 when the luminous flux is completely collimated ideallight.

[0079] Each luminous flux transmitted through the second cylindricalarray homogenizer 307 is guided to the cylindrical condenser lens 309.Since the optical axis of each luminous flux is shifted from the opticalaxis of the cylindrical condenser lens 309, the optical axes of therespective luminous fluxes split by the pupils of the lenses of thearray of the first cylindrical array homogenizer 306 are collected atthe position of a focal line of the cylindrical condenser lens 309.

[0080] The distance between the principal planes of the firstcylindrical array homogenizer 306 and the cylindrical condenser lens 309is set to the sum of the focal length of the first cylindrical arrayhomogenizer 306 and the focal length of the cylindrical condenser lens309. Thus, each luminous flux split by the pupil of each lens of thearray of the first cylindrical array homogenizer 306 is transmittedthrough the cylindrical condenser lens 309 to become collimated light incross section of FIG. 3.

[0081] The width of the collimated light is set to be enlarged at aratio of the focal length of the first cylindrical array homogenizer 306to the focal length of the cylindrical condenser lens 309.

[0082] On the other hand, a modulation surface of the light modulationpanel 312 is disposed at the position of the focal line of thecylindrical condenser lens 309. This achieves an optical integrationoperation on the modulation surface of the light modulation panel 312.Consequently, the luminous flux incident on the illumination opticalsystem is converted to light having generally uniform light intensitydistribution which is irradiated to the modulation surface of the lightmodulation panel 312, irrespective of light intensity distribution atthe time of the incidence.

[0083] Next, description is made for the function of the secondcylindrical array homogenizer 307. The incident luminous flux indicatedby the arrow in FIG. 3 is not completely collimated. Especially, inEmbodiments 1 and 2 which employ the gas exciting light emission sourcerather than a laser, the area for excitation and light emission has afinite area on the order of 0.1 mm at the minimum. Thus, even the use ofa collimating lens or a parabolic reflecting mirror cannot provide acompletely collimated beam, and the aforementioned incident luminousflux always includes divergence (a divergence angle).

[0084] The second cylindrical array homogenizer 307 is provided forcorrecting a blurred outline of an illumination area on the lightmodulation panel 312 due to the divergence error.

[0085] Description is hereinafter made with reference to FIG. 3. Theluminous fluxes split by the pupils of the lenses of the array of thefirst cylindrical array homogenizer 306 have divergence components fromthe entire pupil area. Thus, the pupil images of the lenses of the arrayof the first cylindrical array homogenizer 306 are projected and formedonto the modulation surface of the light modulation panel 312 by therecombination system formed of the second cylindrical array homogenizer307 and the cylindrical condenser lens 309.

[0086] The position of a focal line on the side of light incidence ofeach lens of the array of the second cylindrical array homogenizer 307is set to the pupil position of each lens of the array of the firstcylindrical array homogenizer 306. The divergence components of theluminous fluxes split by the pupils of the lenses of the array of thefirst cylindrical array homogenizer 306 are shown by fine dotted linesin FIG. 3. The luminous fluxes split by the pupils of the lenses of thearray of the first cylindrical array homogenizer 306 are transmitted bythe second cylindrical array homogenizer 307 and thus converted intocollimated light in cross section of FIG. 3. The collimated light iscondensed to focal line plane of the cylindrical condenser lens 309 bythe cylindrical condenser lens 309.

[0087] In other words, the pupil images of the lenses of the array ofthe first cylindrical array homogenizer 306 are superimposed and formedinto images in a state where the images are optically integrated on themodulation surface of the light modulation panel 312. Thus, themodulation surface of the light modulation panel 312 is illuminated bylight which has intensity distribution with sharp edges in cross sectionof FIG. 3.

[0088] (About Shuffling Prism)

[0089] Next, description is made for the shuffling prism serving as theoptical intensity conversion optics incorporated in the illuminationoptical system of Embodiment 1 with reference to FIG. 4.

[0090] In optical elements disposed in FIG. 4, a shuffling prism 303corresponds to the shuffling prism 103 in Embodiment 1. The firstcylindrical lens 305 corresponds to the first cylindrical lens 105 inEmbodiment 1, and the second cylindrical lens 310 corresponds to thesecond cylindrical lens 110 in Embodiment 1. The light modulation panel312 corresponds to the light modulation panel 112 in Embodiment 1.

[0091] Part of a generally collimated luminous flux indicated by anarrow in FIG. 4 is transmitted through the shuffling prism 303. Theshuffling prism 303 has a structure in which opposite surfaces arearranged in parallel with each other, and thus can be considered as acombination of parallel plates. Coarse dotted lines in FIG. 4 showluminous fluxes which pass both over and under the shuffling prism 303in a direction orthogonal to the sheet of FIG. 4, while fine dottedlines show luminous fluxes transmitted within the shuffling prism 303.

[0092] The luminous flux incident on the shuffling prism 303 is shiftedin the up-down direction in FIG. 4 by the opposite parallel surfaces. Ina direction orthogonal to the sheet, the upper half of the incidentluminous flux shown by the arrow is shifted such that the upper endportion is directed to the center. The thickness of the shuffling prism303 is set to achieve the shift.

[0093] Specifically, the upper half of the incident luminous flux isshifted to become the lower half, while the lower half of the incidentluminous flux is shifted to become the upper half. The luminous fluxemerges in this interchanged form. In other words, only the part of theincident luminous flux indicated by the arrow in FIG. 4 and transmittedthrough the shuffling prism 303 emerges as the luminous flux which hasthe central portion and the peripheral portion interchanged, and theupper and lower portions interchanged in the sheet.

[0094] The luminous flux emerging from the shuffling prism 303 is guidedto the first cylindrical lens 305. The first cylindrical lens 305 andthe second cylindrical lens 310 disposed next constitute an afocal beamcompressor of a convex-convex pair.

[0095] The magnification of beam compression is set such that the widthof the compressed incident luminous flux generally matches the effectivewidth of the light modulation panel 312.

[0096] The spacing between the principal planes of the first cylindricallens 305 and the second cylindrical lens 310 is set to the sum of thefocal length of the first cylindrical lens 305 and the focal length ofthe cylindrical lens 310. Thus, in cross section of the sheet of FIG. 4,the luminous flux incident as generally collimated light emerges asgenerally collimated light with an angular magnification correspondingto the reciprocal of the compression magnification and irradiated to thelight modulation panel 312.

[0097] On the other hand, the second cylindrical lens 310 has anotherfunction. The incident luminous flux indicated by the arrow in FIG. 4 isnot completely collimated. Especially, in Embodiment 1 which employs thegas exciting light emission source rather than a laser, the area forexcitation and light emission has a finite area on the order of 0.1 mmat the minimum. Thus, even the use of a collimating lens or a parabolicreflecting mirror cannot provide a completely collimated beam, and theincident luminous flux always includes divergence (a divergence angle).

[0098] The second cylindrical lens 310 has the function of correcting ablurred outline of an illumination area on the light modulation panel312 due to the divergence error.

[0099] The first cylindrical lens 305 transmits the luminous flux withdivergence components from the entire pupil area. Thus, the pupil imageof the first cylindrical lens 305 is projected and formed onto themodulation surface of the light modulation panel 312 by the secondcylindrical lens 310.

[0100] The position of an image-forming conjugate line on the side oflight incidence of the second cylindrical lens 310 is set to the pupilposition of the first cylindrical lens 305. The position of animage-forming conjugate line on the side of light emergence of thesecond cylindrical lens 310 is set to the modulation surface of thelight modulation panel 312. The divergence components of the luminousflux from the pupil of the first cylindrical lens 305 are shown by finedotted lines in FIG. 4. Each luminous flux split by the pupil of thefirst cylindrical lens 305 is transmitted through the second cylindricallens 310 and thus condensed on the modulation surface of the lightmodulation panel 312 in cross section of FIG. 4.

[0101] In other words, the pupil image of the second cylindrical lens310 is transferred and formed into an image on the modulation surface ofthe light modulation panel 312.

[0102] Description is here made for light intensity distribution withwhich the light modulation panel is illuminated by using a combinationof the shuffling prism 303 and the optical integrator described in FIG.3, with reference to FIGS. 6(A) to 6(C) and 7(A) to 7(C).

[0103] FIGS. 6(A) to 6(C) and 7(A) to 7(C) show the process of forminglight intensity distribution on the light modulation panel by theillumination optical system of Embodiment 1. FIGS. 6(A) and 7(A) show across sectional profile of the luminous flux emitted from the lamp unitformed of the gas exciting light source and the parabolic reflectingmirror. In FIG. 6(A), a brighter portion indicates a higher lightintensity. In FIG. 7(A), a solid line shows light intensity distributionin cross section in a horizontal (X) direction at the center (0 mm) in avertical (Y) direction of FIG. 6(A), while a dotted line shows lightintensity distribution in cross section in the vertical (Y) direction atthe center (0 mm) in the horizontal (X) direction of FIG. 6(A).

[0104] The light intensity distribution of the luminous flux shown inFIGS. 6(A) and 7(A) is converted into a cross sectional profile of theluminous flux shown in FIGS. 6(B) and 7(B) by the shuffling prism andthe reflecting mirror which reverse the distribution at the centralportion and the peripheral portion in the central area of the luminousflux and also reverse the distribution on the left and right.

[0105] In FIG. 6(B), areas sectioned by horizontal lines correspond tothe areas split and integrated by the optical integrator. Finally, lightintensity distribution shown in FIGS. 6(C) and 7(C) can be provided onthe modulation surface of the light modulation panel.

[0106] As can be seen from FIGS. 6(C) and 7(C), the light intensitydistribution of the illumination luminous flux incident on themodulation surface of the light modulation panel has high intensity andis generally flat (uniform).

[0107] It goes without saying, however, that the ray densitydistribution on the modulation surface of the light modulation panel canbe changed in accordance with a purpose by designing the thickness ofthe shuffling prism in the direction of optical integration, the numberof the shuffling prisms, or the shift amount of the luminous flux topredetermined values. In this manner, the illumination luminous fluxincident on the modulation surface of the light modulation panel can beintentionally provided with predetermined light intensity distributionin the direction in which the light intensity conversion optics exertthe effect.

[0108] Next, description is made for the optics which convert lightintensity distribution incorporated in the illumination optical systemof Embodiment 2 with reference to FIG. 5.

[0109] In optical elements in FIG. 5, a first cylindrical lens 405corresponds to the first cylindrical lens 205 in Embodiment 2, and thesecond cylindrical lens 410 corresponds to the second cylindrical lens210 in Embodiment 2. The light modulation panel 412 corresponds to thelight modulation panel 212 in Embodiment 2.

[0110] A generally collimated luminous flux indicated by an arrow inFIG. 5 is incident on the first cylindrical lens 405. The firstcylindrical lens 405 and the second cylindrical lens 410 disposed nextconstitute an afocal beam compressor of a convex-convex pair. Themagnification of beam compression is set such that the width of thecompressed incident luminous flux substantially matches the effectivewidth of the light modulation panel 312.

[0111] The spacing between the principal planes of the first cylindricallens 405 and the second cylindrical lens 410 is set to the sum of thefocal length of the first cylindrical lens 405 and the focal length ofthe second cylindrical lens 410. Thus, in cross section of the sheet ofFIG. 5, the luminous flux incident as the generally collimated lightemerges as generally collimated light with an angular magnificationcorresponding to the reciprocal of the compression magnification andirradiated to the light modulation panel 412.

[0112] On the other hand, the second cylindrical lens 410 has anotherfunction. The incident luminous flux indicated by the arrow in FIG. 5 isnot completely collimated. Especially, in Embodiment 2 which employs thegas exciting light emission source rather than a laser, the area forexcitation and light emission has a finite area on the order of 0.1 mmat the minimum. Thus, even the use of a collimating lens or a parabolicreflecting mirror cannot provide a completely collimated beam, and theincident luminous flux always includes divergence (a divergence angle).

[0113] The second cylindrical lens 410 has the function of correcting ablurred outline of an illumination area on the light modulation panel412 due to the divergence error.

[0114] The first cylindrical lens 405 transmits the luminous flux withdivergence components from the entire pupil area. The pupil image of thefirst cylindrical lens 405 is projected and formed onto a modulationsurface of the light modulation panel 412 by the second cylindrical lens410.

[0115] The position of an image-forming conjugate line on the side oflight incidence of the second cylindrical lens 410 is set to the pupilposition of the first cylindrical lens 405. The position of animage-forming conjugate line on the side of light emergence of thesecond cylindrical lens 410 is set to the modulation surface of thelight modulation panel 412. The divergence components of the luminousflux from the pupil of the first cylindrical lens 405 are shown by finedotted lines in FIG. 5. Each luminous flux split by the pupil of thefirst cylindrical lens 405 is transmitted through the second cylindricallens 410 and thus condensed on the modulation surface of the lightmodulation panel 412 in cross section of FIG. 5. In other words, thepupil image of the second cylindrical lens 410 is transferred and formedinto an image on the modulation surface of the light modulation panel412.

[0116] The beam compressor formed of the first cylindrical lens 405 andthe second cylindrical lens 410 is an afocal optical system. Pupildistortion aberration, also referred to as spherical aberration in anafocal system, is intentionally provided as aberration caused by thepupil image transfer by the beam compressor. Each cylindrical surface ofthe first cylindrical lens 405 and the second cylindrical lens 410 has asmall curvature and is designed to produce more aberration in accordancewith a shift amount from the optical axis. As shown by coarse dottedlines in FIG. 5, rays close to the optical axis are transmitted throughthe second cylindrical lens 410 and then converted to a slightlydivergent luminous flux in cross section of the sheet of FIG. 5.

[0117] On the other hand, rays on the periphery of the pupil away fromthe optical axis are transmitted through the second cylindrical lens 410and then converted to a slightly convergent luminous flux in crosssection of the sheet of FIG. 5. Since the changes of divergence andconvergence are continuously and smoothly provided in this manner, theray density is low at the central portion and high at the peripheralportion on the modulation surface of the light modulation panel 412 incross section of the sheet of FIG. 5. Light intensity distributionilluminating the modulation surface of the light modulation panel 412 isprovided by multiplying light intensity distribution of the incidentluminous flux indicated with the arrow from the lamp unit formed of thegas exciting light source and the parabolic reflecting mirror by theaforementioned ray density distribution.

[0118] Description is here made for light intensity distribution withwhich the light modulation panel is illuminated by using a combinationof the light intensity conversion optics and the optical integratordescribed in FIG. 3, with reference to FIGS. 8(A) to 8(C) and 9(A) to9(C).

[0119] FIGS. 8(A) to 8(C) and 9(A) to 9(C) show the process of forminglight intensity distribution on the light modulation panel by theillumination optical system of Embodiment 2. FIGS. 8(A) and 9(A) show across sectional profile of the luminous flux emitted from the lamp unitformed of the gas exciting light source and the parabolic reflectingmirror. In FIG. 8(A), a brighter portion indicates a higher lightintensity. In FIG. 9(A), a solid line shows light intensity distributionin cross section in a horizontal (X) direction at the center (0 mm) in avertical (Y) direction in FIG. 8(A), while a dotted line shows lightintensity distribution in cross section in the vertical (Y) direction atthe center (0 mm) in the horizontal (X) direction in FIG. 8(A).

[0120] The light intensity distribution shown in FIGS. 8 (A) and 9(A) isdivided and integrated by the optical integrator in areas sectioned byhorizontal lines in FIG. 8(A). Then, ray density distribution on themodulation surface of the light modulation panel shown in FIG. 8(B)resulting from the aforementioned pupil distortion aberration of thebeam compressor is multiplied in the direction of the light intensityconversion optics to provide light intensity distribution on themodulation surface of the light modulation panel shown in FIGS. 8(C) and9(C).

[0121] As can be seen from FIGS. 8(C) and 9(C), the light intensitydistribution of the illumination luminous flux incident on themodulation surface of the light modulation panel has high intensity andis generally flat (uniform).

[0122] It goes without saying, however, that the ray densitydistribution on the modulation surface of the light modulation panel canbe changed in accordance with a purpose by designing the pupildistortion aberration of the beam compressor to a predetermined value.In this manner, the illumination luminous flux incident on themodulation surface of the light modulation panel can be intentionallyprovided with predetermined light intensity distribution in thedirection in which the light intensity conversion optics exert theeffect.

[0123] Next, characteristics provided by the illumination optical systemexplained so far are described with reference to FIGS. 10(A) to 10(C)and 11(A) to 11(C).

[0124] FIGS. 11(A) to 11(C) show incident angle distribution of rayssubjected to optical integration operation by a conventional pair oftwo-dimensional fly eye lens arrays on an illumination surface such as amodulation surface of a light modulation panel. In FIG. 11(A), the outerperiphery of a circle corresponds to azimuth angles of 360 degrees, andradial axes show elevation angles with respect to the normal to theillumination surface (a perpendicular incident axis). In FIG. 11(A), theouter periphery is divided by the radial axes in elevation angles of 20degrees. FIGS. 11(B) and 11(C) show light intensity distribution takenalong a line B-B and a line C-C in FIG. 11(A), respectively.

[0125] On the other hand, FIGS. 10(A) to 10(C) show incident angledistribution of rays provided by the illumination optical system ofEmbodiment 2 on an illumination surface such as a modulation surface ofa light modulation panel. In FIG. 10(A), the outer periphery of a circlecorresponds to azimuth angles of 360 degrees, and radial axes showangles of incident on the illumination surface. In FIG. 10(A), the outerperiphery is divided by the radial axes in elevation angles of 20degrees. FIGS. 10(B) and 10(C) show light intensity distribution takenalong a line B-B and a line C-C in FIG. 10(A), respectively.

[0126] As can be seen from comparison between FIG. 10(A) and 11(A), theluminous flux irradiated to the illumination surface can have generallyuniform light intensity distribution on the illumination surface in bothcases. However, a large difference is found between them in incidentangle characteristics of a luminous flux.

[0127] Specifically, as shown in FIG. 11(A), the illumination luminousflux subjected to the optical integration operation by the pair oftwo-dimensional fly eye lens arrays has symmetrical ray distribution intwo directions of the azimuth on the illumination surface.

[0128] In contrast, in the present embodiment, as shown in FIG. 10(A),ray incident elevation angles in the optical integration direction (B-Bdirection) vertical in FIG. 10(A) are similar to those in FIG. 11(A),while in the direction in which the light intensity conversion opticsexert the effect (C-C direction), no luminous fluxes are superimposed byoptical integration operation, so that elevation angles dependent on theangular magnification determined by the compression magnification of thebeam compressor are provided with respect to the divergent angle of theluminous flux emitted from the lamp unit. Thus, the ray incident angleon the illumination surface can be significantly reduced in thedirection in which the light intensity conversion optics exert theeffect.

[0129] Specifically, an illumination method is used in which, in theintensity distribution of illumination light on the illumination surfacechanging depending on the deviation angle of the incident ray withrespect to the normal to the illumination surface, a ratio α:β is anaspect ratio of 2:1 or higher, where α and β represent angle widths atwhich the light intensity reaches half of a peak value P (1/2P) in eachof two directions (B-B axis and C-C axis) orthogonal to each other onthe illumination surface.

[0130] More specifically, the angle width at which the light intensityreaches half of the peak value on the B-B axis is twice or more theangle width at which the intensity reaches half of the peak value on theC-C axis. Alternatively, the maximum value of the angle width at whichthe light intensity reaches half of the peak value in the B-B axisdirection may be set to be twice or more the maximum value of the anglewidth at which the light intensity reaches half of the peak value in theC-C axis direction.

[0131] Description is hereinafter made for influences (advantages)exerted by the aforementioned characteristics on a projection type imagedisplay apparatus which employs the illumination optical systemdescribed above in Embodiments 3 to 6.

Embodiment 3

[0132]FIG. 12 shows the overall projection display optical system in aprojection type image display apparatus which is Embodiment 3 of thepresent invention.

[0133] In FIG. 12, reference numeral 1 schematically shows theillumination optical system described in Embodiments 1 and 2. Arepresentation on the left in the frame in the figure shows theillumination optical system on the right viewed from an arrow D.

[0134] Reference numeral 2 shows a reflection type liquid crystalmodulation panel (hereinafter referred to as a liquid crystal modulationpanel). Reference numeral 3 shows a light modulation panel driver whichconverts an external video input signal from an image information supplyapparatus such as a personal computer, a television, a VCR, and a DVDplayer, not shown, into a driving signal for driving the liquid crystalmodulation panel 2. The liquid crystal modulation panel 2 forms anoriginal image with liquid crystal corresponding to the driving signalinput thereto to modulate an illumination luminous flux incident on theliquid crystal modulation panel 2.

[0135] Reference numeral 10 shows a polarization beam splitter whichreflects, of illumination light from the illumination optical system 1,linearly polarized light polarized in a direction orthogonal to thesheet of FIG. 12 by a polarization splitting surface (reflectsS-polarized light) and guides the polarized light to the liquid crystalmodulation panel 2.

[0136] The illumination light incident on the liquid crystal modulationpanel 2 (the linearly polarized light in the direction orthogonal to thesheet) is given a phase difference of the polarization in accordancewith the modulation state of pixels arranged in the liquid crystalmodulation panel 2. Light components in a direction in parallel with thesheet are transmitted as P-polarized light through the polarizationsplitting surface of the polarization beam splitter 10, while lightcomponents in the direction orthogonal to the sheet are reflected asS-polarized light by the polarization splitting surface of thepolarization beam splitter 10 and return toward the illumination opticalsystem 1.

[0137] The light components as P-polarized light transmitted through thepolarization splitting surface of the polarization beam splitter 10 aretaken by the entrance pupil of a projection lens 4 without any change.Since the projection lens 4 is arranged to dispose a modulation surfaceof the liquid crystal modulation panel 2 and a diffusion surface of alight diffusion screen 5 in an optically conjugate relationship, theoriginal image formed on the modulation surface of the liquid crystalmodulation panel 2 is projected and displayed as an image (an imagecorresponding to the video signal) on the light diffusion screen 5.

[0138] The polarization beam splitter 10 is a typically usedpolarization beam splitter of a MacNeil type and has the polarizationsplitting surface for S-polarized light and P-polarized light by meansof the Brewster angle. In the polarization beam splitter 10, as adeviation amount of the incident angle of a ray from 45 degrees withrespect to the polarization splitting surface is increased, accuracy ofsplitting of S-polarized light and P-polarized light is suddenlyreduced. The accuracy of splitting of S-polarized light and P-polarizedlight can be actually maintained at a ratio of approximately 50:1 when adeviation amount from 45 degrees falls within approximately ±3 degrees.

[0139] If the optical integrator implemented by the conventional pair oftwo-dimensional fly eye lens arrays is used in the illumination opticalsystem, the luminous flux with the incident angle distribution as shownin FIG. 11(A) is incident on the polarization beam splitter 10. Thisproduces the disadvantage that, of luminous fluxes with a deviationamount of incident angle of ±3 degrees or more from 45 degrees withrespect to the polarization splitting surface, a proportion ofP-polarized light is reflected, and a proportion of S-polarized light istransmitted.

[0140] The polarized light is given a phase difference in accordancewith the modulation state of pixels arranged in the liquid crystalmodulation panel 2. However, when the liquid crystal panel 2 sendslinearly polarized light (modulated light) polarized in the directionorthogonal to the sheet of FIG. 12 to display black on the screen, aluminous flux inclined three degrees or more from 45 degrees withrespect to the polarization splitting surface of the polarization beamsplitter 10 includes a proportion of S-polarized light which istransmitted through the surface and reaches the light diffusion screen 5through the projection lens 4. As a result, the intended black isdisplayed in gray to reduce illuminance contrast.

[0141] For the polarized light modulation characteristics of the liquidcrystal modulation panel 2, when twisted nematic liquid crystal is usedin the liquid crystal modulation panel 2, the liquid crystal modulationpanel 2 fundamentally has the characteristic that it cannot accuratelyprovide a phase difference for polarized light incident on the liquidcrystal modulation panel 2 at an azimuth of 45 degrees. For this reason,in the optical integrator implemented by the conventional pair oftwo-dimensional fly eye lens arrays which illuminates light from azimuthgenerally symmetrical with respect to the axis, polarized lightmodulation by the liquid crystal is not sufficient, and intended blackdisplay is shown in gray to reduce illuminance contrast, similarly tothe incident angle dependency characteristics of the polarization beamsplitter 10 described above.

[0142] In contrast, in the projection type image display apparatus ofEmbodiment 3, the illumination optical system 1 of Embodiments 1 and 2can be used to provide a luminous flux with the incident angledistribution as shown in FIG. 10(A). When the luminous flux is incidenton the polarization beam splitter 10, a deviation amount of the incidentangle from 45 degrees with respect to the polarization splitting surfacefalls within ±3 to 4 degrees. This can almost eliminate a reduction inilluminance contrast due to the polarization splitting error which meansthat polarization splitting does not match the modulation state of thepixels in the liquid crystal modulation panel occurring when the opticalintegrator implemented by the conventional pair of two-dimensional flyeye lens arrays is used.

[0143] For the liquid crystal modulation panel 2, since almost nocomponents of illumination luminous fluxes are directed from an azimuthat which polarized light modulation by the liquid crystal is notsufficiently achieved, a reduction in illuminance contrast is almosteliminated, similarly to the incident angle dependency characteristicsof the polarization beam splitter 10 described above.

Embodiment 4

[0144]FIG. 13 shows the overall projection display optical system in aprojection type image display apparatus which is Embodiment 4 of thepresent invention.

[0145] In FIG. 13, reference numeral 1 schematically shows theillumination optical system described in Embodiments 1 and 2. Arepresentation on the left in the frame in the figure shows theillumination optical system on the right viewed from an arrow D. InEmbodiment 4, the illumination optical system 1 does not need to includethe polarization conversion element arrays 108 and 208.

[0146] Reference numeral 2M shows a mirror array light deflectionmodulation panel (hereinafter referred to as a mirror modulation panel).Reference numeral 3 shows a light modulation panel driver which convertsan external video input signal from an image information supplyapparatus such as a personal computer, a television, a VCR, and a DVDplayer, not shown, into a driving signal for driving the mirrormodulation panel 2M. The mirror modulation panel 2M deflects and driveseach micromirror pixel corresponding to the driving signal input theretoto deflect and modulate illumination luminous fluxes incident on themirror modulation panel 2M.

[0147] Reference numeral 11 shows a total reflection tilt prism whichreflects illumination light from the illumination optical system 1 by atotal reflection surface and directs the light to illuminate the mirrormodulation panel 2M obliquely to the normal thereof. In this case, themicromirror pixels arranged in the mirror modulation panel 2M aredeflected in the plane which includes the normal to the mirrormodulation panel 2M and the optical axis of the illumination light.

[0148] The illumination light incident on the mirror modulation panel 2Mis reflected in a controlled direction in accordance with the modulationstate of the micromirror pixels in the mirror modulation panel 2M.Specifically, the light is deflected and modulated to reflect the lightto the outside of the pupil area of a projection lens 4 for blackmodulation, while the light is deflected and modulated to reflect thelight into the pupil area of the projection lens 4 for white modulation.In white modulation, the light is deflected to be incidentperpendicularly to the total reflection surface of the total reflectiontilt prism 11, so that the light is transmitted through the totalreflection surface and through a prism 12 for correcting an optical pathlength disposed with an air gap between them, and then taken by theentrance pupil of the projection lens 4 without any change.

[0149] Since the projection lens 4 is arranged to dispose a modulationsurface of the mirror modulation panel 2M and a diffusion surface of alight diffusion screen 5 in an optically conjugate relationship, themodulated light is projected onto the light diffusion screen 5 todisplay an image corresponding to the video signal on the lightdiffusion screen 5.

[0150] As the illumination luminous flux has a smaller convergent angle,the total reflection surface of the total reflection tilt prism 11 candirect the luminous flux closer to be perpendicular to the mirrormodulation panel 2M. In addition, as the illumination luminous flux hasa smaller convergent angle, modulation can be performed at a smallerdeflection angle of the micromirror pixels in the mirror modulationpanel 2M. Thus, design can be performed with relaxed limitations onarrangement of the overall optical system in terms of device and with alarger latitude in terms of size. As a result, the entire apparatus canbe manufactured with low cost.

[0151] Therefore, when the optical integrator implemented by theconventional pair of two-dimensional fly eye lens arrays is used in theillumination optical system, a luminous flux with the incident angledistribution as shown in FIG. 11(A) has an convergent angle, so that theaforementioned advantages are difficult to achieve.

[0152] In contrast, the use of the illumination optical system 1 ofEmbodiments 1 and 2 can provide a luminous flux with the incident angledistribution as shown in FIG. 10(A), thereby allowing the aforementionedadvantages.

Embodiment 5

[0153]FIG. 14 shows the overall projection display optical system in aprojection type image display apparatus which is Embodiment 5 of thepresent invention.

[0154] In FIG. 14, reference numeral 1 schematically shows theillumination optical system described in Embodiments 1 and 2. Arepresentation on the left in the frame in the figure shows theillumination optical system on the right viewed from an arrow D.

[0155] Reference numerals 2R, 2G, and 2B show transmission type liquidcrystal modulation panels (hereinafter referred to as liquid crystalmodulation panels) for read, green, and blue, respectively. Referencenumeral 3 shows a light modulation panel driver which converts anexternal video input signal from an image information supply apparatussuch as a personal computer, a television, a VCR, and a DVD player, notshown, into a driving signal for driving the liquid crystal modulationpanels 2R, 2G, and 2B. Each of the liquid crystal modulation panels 2R,2G, and 2B forms an original image with liquid crystal corresponding tothe driving signal input thereto to modulate an illumination luminousflux incident on each of the liquid crystal modulation panels 2R, 2G,and 2B.

[0156] Reference numeral 20 shows a red splitting dichroic mirror whichreflects light components for red and transmits light components forcyan (green and blue), of illumination light as linearly polarized lightpolarized in a direction orthogonal to the sheet from the illuminationoptical system 1. The light components for red reflected by the redsplitting dichroic mirror 20 are guided to the liquid crystal modulationpanel 2R for red by a mirror 22.

[0157] On the other hand, of the light components for cyan transmittedthrough the red splitting dichroic mirror 20, light components for greenwhich corresponds to light components for yellow are reflected by ayellow splitting dichroic mirror 21 and guided to the liquid crystalmodulation panel 2G for green.

[0158] Light components for blue transmitted through the yellowsplitting dichroic mirror 21 are guided to the liquid crystal modulationpanel 2B for blue by two mirrors 23 and 24. In the optical path for theblue light components transmitted through the yellow splitting dichroicmirror 21, a cat's-eye optical system formed of Fourier transform lenses25 and 26 is provided to extend the optical path length to transfer thepupil to the liquid crystal modulation panel 2B for blue.

[0159] In this manner, the respective liquid crystal modulation panels2R, 2G, and 2B are illuminated by the corresponding color lightcomponents.

[0160] The illumination light components for the respective colorsincident on the liquid crystal modulation panels 2R, 2G, and 2B (thelinearly polarized light polarized in the direction orthogonal to thesheet) are given phase differences of polarization in accordance withthe modulation state of pixels arranged in the liquid crystal modulationpanels 2R, 2G, and 2B.

[0161] The modulated light emerging from each of the liquid crystalmodulation panels 2R, 2G, and 2B is incident on an analyzer (not shown)attached to an incident surface for each color component of a crossdichroic prism 13 serving as a color combination prism. In this case,modulated light components polarized in the direction orthogonal to thesheet are transmitted through the analyzer, while modulated lightcomponents polarized in a direction in parallel with the sheet areabsorbed by the analyzer and lost as heat.

[0162] The modulated light component for each color transmitted througheach analyzer (the modulated light component polarized in the directionorthogonal to the sheet) is incident on the cross dichroic prism 13.

[0163] The cross dichroic prism 13 is formed by arranging a redreflecting dichroic film and a blue reflecting dichroic film in a crossshape to exert effects on S-polarized light such that the formerreflects red light and transmits green light and blue light and thelatter reflects blue light and transmits green light and red light.

[0164] The cross dichroic prism 13 is used to reflect the image light(the modulated light) for red by the red reflecting dichroic film towarda projection lens 4 and reflect the image light for blue by the bluereflecting dichroic film toward the projection lens 4. The image lightfor green is transmitted both of the dichroic films and directed towardthe projection lens 4.

[0165] The liquid crystal modulation panels 2R, 2G, and 2B are adjustedor mechanically or electrically compensated for such that predeterminedpixels on the respective panels are relatively superimposed on the lightdiffusion screen 5 with high accuracy.

[0166] The light components for the respective colors combined by thecross dichroic prism 13 are taken by the entrance pupil of theprojection lens 4. The projection lens 4 is arranged to dispose amodulation surface of each liquid crystal modulation panel and adiffusion surface of the light diffusion screen 5 in an opticallyconjugate relationship. Thus, the light components for the respectivecolors combined by the cross dichroic prism 13 are transferred to thelight diffusion screen 5 to project and display an image correspondingto the video signal on the light diffusion screen 5.

[0167] As the color combination prism, a 3P (piece) prism or a 4P prismmay be used other than the aforementioned cross dichroic prism 13.

[0168] Each of the dichroic mirrors 20 and 21 used for illuminating theliquid crystal modulation panels 2R, 2G, and 2B, and the dichroic filmdisposed in the cross dichroic prism 13 which combines the modulatedlight components for the respective colors have the characteristic that,as a deviation amount of the incident angle of a ray from 45 degreeswith respect to the dichroic film is increased, the splitting wavelengthis shifted toward a shorter wavelength at an obtuse angle or toward alonger wavelength at an acute angle.

[0169] Thus, when the optical integrator implemented by the conventionalpair of two-dimensional fly eye lens arrays is used in the illuminationoptical system, a luminous flux with the incident angle distribution asshown in FIG. 11(A) is incident on the dichroic film, so that luminousfluxes at different wavelengths coexist as the incident angle isdeviated from 45 degrees with respect to the dichroic film. In thiscase, if the lamp unit has gradual radiation energy wavelengthdistribution like blackbody radiation, distribution of angles incidenton the dichroic film is symmetric about 45 degrees, so that the averagecut wavelength is not changed. However, when the lamp unit of electronexcited radiation which uses gas exciting light emission is used, it haswavelength spectral distribution including emission lines as dominantparts in radiation energy wavelength distribution, and thus the averagecut wavelength is changed with the median point.

[0170] Therefore, color combination by the dichroic films is notappropriately achieved to result in poor color reproducibility in aprojected image.

[0171] For the polarized light modulation characteristics of the liquidcrystal modulation panels 2R, 2G, and 2B which are the transmission typeliquid crystal modulation elements, when twisted nematic liquid crystalis used as the liquid crystal modulation element, it fundamentally hasthe characteristic that it cannot accurately provide a phase differencefor modulation of polarized light incident on the transmission typeliquid crystal at an azimuth of 45 degrees. For this reason, in theoptical integrator implemented by the conventional pair oftwo-dimensional fly eye lens arrays which illuminates light fromazimuths generally symmetric with respect to the axis, polarizationmodulation by the liquid crystal is not sufficient, and intended blackdisplay is shown in gray to reduce illuminance contrast.

[0172] On the contrary, the illumination optical system 1 of Embodiments1 and 2 can be used to provide a luminous flux with the incident angledistribution as shown in FIG. 10(A). When the luminous flux is incidenton the dichroic film, a deviation amount of the incident angle from 45degrees with respect to the dichroic film falls within ±3 to 4 degrees.This can almost eliminate inappropriate color combination due to thechange in the average cut wavelength with the median point in thedichroic film occurring when the optical integrator implemented by theconventional pair of two-dimensional fly eye lens arrays is used.

[0173] For the polarized light modulation characteristics of therespective liquid crystal modulation panels 2R, 2G, and 2B, since almostno components of illumination luminous fluxes are directed from anazimuth at which polarized light modulation by the liquid crystal is notsufficiently achieved, a reduction in illuminance contrast is almosteliminated.

Embodiment 6

[0174]FIG. 15 shows the overall projection display optical system in aprojection type image display apparatus which is Embodiment 6 of thepresent invention.

[0175] In FIG. 15, reference numeral 1 schematically shows theillumination optical system described in Embodiments 1 and 2. Arepresentation on the left in the frame in the figure shows theillumination optical system on the right viewed from an arrow D.

[0176] Reference numerals 2R, 2G, and 2B show reflection type liquidcrystal modulation panels (hereinafter referred to as liquid crystalmodulation panels) for read, green, and blue, respectively. Referencenumeral 3 shows a light modulation panel driver which converts anexternal video input signal from an image information supply apparatussuch as a personal computer, a television, a VCR, and a DVD player, notshown, into a driving signal for driving the liquid crystal modulationpanels 2R, 2G, and 2B. Each of the liquid crystal modulation panels 2R,2G, and 2B forms an original image with liquid crystal corresponding tothe driving signal input thereto to reflect and modulate an illuminationluminous flux incident on each of the liquid crystal modulation panels2R, 2G, and 2B.

[0177] Of illumination light as linearly polarized light polarized in adirection orthogonal to the sheet of FIG. 16 from the illuminationoptical system 1, light components for magenta (red and blue) arereflected by a magenta splitting dichroic mirror 30 which reflects thelight components for magenta and transmits light components for green.

[0178] The reflected light components for magenta are incident on a bluecross color polarizer 34 which provides a phase difference of π forpolarized light for blue. This produces light components for blue whichare linearly polarized light polarized in a direction in parallel withthe sheet and light components for red which are linearly polarizedlight polarized in the direction orthogonal to the sheet.

[0179] The blue light components and the red light components areincident on a polarization beam splitter 33 in which the blue lightcomponents which are P-polarized light are transmitted through apolarization splitting film and guided to the liquid crystal modulationpanel 2B for blue. The red light components which are S-polarized lightare reflected by the polarization splitting film and guided to theliquid crystal modulation panel 2R for red.

[0180] On the other hand, the green light components transmitted throughthe magenta splitting dichroic mirror 30 are transmitted through a dummyglass 36 for correcting an optical path length and incident on apolarization beam splitter 31.

[0181] The green light components which are S-polarized light incidenton the polarization beam splitter 31 are reflected by a polarizationsplitting film of the polarization beam splitter 31 and guided to theliquid crystal modulation panel 2G for green.

[0182] In this manner, the respective liquid crystal modulation panels2R, 2G, and 2B are illuminated by the corresponding color lightcomponents.

[0183] The illumination light components for the respective colorsincident on the liquid crystal modulation panels 2R, 2G, and 2B (thelinearly polarized light polarized in the direction orthogonal to thesheet) are given phase differences of polarization in accordance withthe modulation state of pixels arranged in the liquid crystal modulationpanels 2R, 2G, and 2B.

[0184] Of the modulated light emerging from the liquid crystalmodulation panels 2R, 2G, and 2B, light components polarized in the samedirection as the illumination light return toward the lamp unit alongthe optical path reversely to the illumination. Light componentspolarized in a direction orthogonal to the polarization direction of theillumination light reach a projection lens 4 as follows.

[0185] Specifically, the light modulated by the liquid crystalmodulation panel 2R for red is converted into P-polarized lightpolarized in the direction in parallel with the sheet and is transmittedthrough the polarization splitting film of the polarization beamsplitter 33. Next, the light is transmitted through a red cross colorpolarizer 35 which provides a phase difference of π for the polarizedlight for red, and is converted into light components for red aslinearly polarized light polarized in the direction orthogonal to thesheet.

[0186] The red light components which have been converted intoS-polarized light are incident on a polarization beam splitter 32,reflected by a polarization splitting film thereof, and directed towardthe projection lens 4.

[0187] The light modulated by the liquid crystal modulation panel 2B forblue is converted into S-polarized light polarized in the directionorthogonal to the sheet and reflected by the polarization splitting filmof the polarization beam splitter 33. Then, the light is transmittedthrough the red cross color polarizer 35 without being subjected to theeffect of the polarizer 35 and incident on the polarization beamsplitter 32.

[0188] The blue light components which are S-polarized light arereflected by the polarization splitting film of the polarization beamsplitter 32 and directed toward the projection lens 4.

[0189] The light modulated by the liquid crystal modulation panel 2G forgreen is converted into P-polarized light polarized in the direction inparallel with the sheet and transmitted through the polarizationsplitting film of the polarization beam splitter 31. The light istransmitted through a dummy glass 37 for correcting an optical pathlength and incident on the polarization beam splitter 32. The greenlight components which are P-polarized light are transmitted through thepolarization splitting film of the polarization beam splitter 32 anddirected toward the projection lens 4.

[0190] The liquid crystal modulation panels 2R, 2G, and 2B are adjustedor mechanically or electrically compensated for such that predeterminedpixels on the respective panels are relatively superimposed on a lightdiffusion screen 5 with high accuracy.

[0191] The light components for the respective colors combined by thepolarization beam splitter 32 are taken by the entrance pupil of theprojection lens 4. The projection lens 4 is arranged to dispose amodulation surface of each liquid crystal modulation panel and adiffusion surface of the light diffusion screen 5 in an opticallyconjugate relationship. Thus, the light components for the respectivecolors combined by the polarization beam splitter 32 are transferred tothe light diffusion screen 5 to project and display an imagecorresponding to the video signal on the light diffusion screen 5.

[0192] The dichroic film of the dichroic mirror 30 used in the opticalpath for illuminating the liquid crystal modulation panels 2R, 2G, and2B has the characteristic that, as a deviation amount of the incidentangle of a ray from 45 degrees with respect to the dichroic film isincreased, the splitting wavelength is shifted toward a shorterwavelength at an obtuse angle or toward a longer wavelength at an acuteangle.

[0193] Thus, when the optical integrator implemented by the conventionalpair of two-dimensional fly eye lens arrays is used in the illuminationoptical system, a luminous flux with the incident angle distribution asshown in FIG. 11(A) is incident on the dichroic film, so that luminousfluxes at different wavelengths coexist as the incident angle isdeviated from 45 degrees with respect to the dichroic film.

[0194] If the lamp unit serving as the light source has gradualradiation energy wavelength distribution like blackbody radiation, thedistribution of angles incident on the dichroic film is symmetric about45 degrees, so that the average cut wavelength is not changed. However,when the lamp unit of electron excited radiation which uses gas excitinglight emission is used as in Embodiment 6, it has wavelength spectraldistribution including emission lines as dominant parts in radiationenergy wavelength distribution, and thus the average cut wavelength ischanged with the median point. Therefore, color splitting by thedichroic films is not appropriately achieved to result in thedisadvantage of unnatural color reproducibility in a projected image.

[0195] The polarization beam splitters 31, 32, and 33 used in theoptical path for illuminating the liquid crystal modulation panels 2R,2G, and 2B and the optical path for color combination are typicalpolarization beam splitters of a MacNeil type, and have the polarizationsplitting films for S-polarized light and P-polarized light by means ofthe Brewster angle. As a deviation amount of the incident angle of a rayfrom 45 degrees with respect to the polarization splitting surface isincreased, accuracy of splitting of S-polarized light and P-polarizedlight is suddenly reduced.

[0196] The accuracy of splitting of S-polarized light and P-polarizedlight can be actually maintained at a ratio of approximately 50:1 when adeviation amount from 45 degrees falls within approximately ±3 degrees.Thus, when the optical integrator implemented by the conventional pairof two-dimensional fly eye lens arrays is used, a luminous flux with theincident angle distribution as shown in FIG. 11(A) is incident on thepolarization beam splitters 31 and 32. In addition, the luminous flux isincident on the polarization beam splitters 31, 32, and 33 after thereflection and polarized light modulation by the liquid crystalmodulation panels 2R, 2G, and 2B. This produces the disadvantage that,of luminous fluxes with a deviation amount of incident angle of ±3degrees or more from 45 degrees with respect to the polarizationsplitting surface, a portion of P-polarized light is reflected, and aportion of S-polarized light is transmitted.

[0197] The illumination light incident on each of the liquid crystalmodulation panels 2R, 2G, and 2B formed of reflection type liquidcrystal display element is given a phase difference of polarization inaccordance with the modulation state of pixels arranged in each of theliquid crystal modulation panels 2R, 2G, and 2B. However, even when theliquid crystal modulation panels 2R, 2G, and 2B sends light which is notsubjected to a change in phase difference to display black, a luminousflux inclined three degrees or more from 45 degrees with respect to thepolarization splitting surface of the polarization beam splitters 31 to33 includes a portion of P-polarized light which is reflected and aportion of S-polarized light which is transmitted and transferred to thelight diffusion screen 5 through the projection lens 4. As a result, theintended black is displayed in gray to reduce illuminance contrast.

[0198] For the polarized light modulation characteristics of the liquidcrystal modulation panels 2R, 2G, and 2B, when twisted nematic liquidcrystal is used in the liquid crystal modulation panels, the liquidcrystal modulation panels 2R, 2G, and 2B fundamentally have thecharacteristic that it cannot accurately modulate light incident on thereflection type liquid crystal modulation panels at an azimuth of 45degrees. For this reason, in the optical integrator implemented by theconventional pair of two-dimensional fly eye lens arrays whichilluminates light from azimuths generally symmetric with respect to theaxis, polarization modulation of the liquid crystal is not sufficient,and intended black display is shown in gray to reduce illuminancecontrast, similarly to the incident angle dependency characteristics ofthe polarization beam splitters 31 to 33 described above.

[0199] To address these disadvantages, the illumination optical system 1of Embodiments 6 can be used to provide a luminous flux with theincident angle distribution as shown in FIG. 10(A). When the luminousflux is incident on the dichroic mirror 30, a deviation amount of theincident angle from 45 degrees with respect to the dichroic film fallswithin ±3 to 4 degrees. This can almost eliminate inappropriate colorcombination in the color splitting by the dichroic film due to thechange in the average cut wavelength with the median point to result inpoor color reproducibility in a projected image occurring when theoptical integrator implemented by the conventional pair oftwo-dimensional fly eye lens arrays is used.

[0200] When the luminous flux is incident on the polarization beamsplitter 31 to 33, a deviation amount of the incident angle from 45degrees with respect to each polarization splitting surface falls within±3 to 4 degrees. This can almost eliminate a reduction in illuminancecontrast due to the polarization splitting error which means thatpolarization splitting does not match the modulation state of the pixelsin the liquid crystal modulation panel occurring when the opticalintegrator implemented by the conventional pair of two-dimensional flyeye lens arrays is used.

[0201] For the disadvantage in providing the phase difference for themodulation of polarized light depending on the incident angle on thereflection type liquid crystal modulation panel, since almost nocomponents of illumination luminous fluxes are directed from an azimuthat which polarized light modulation by the liquid crystal is notsufficiently achieved, a reduction in illuminance contrast can be almosteliminated.

[0202] The projection type image display apparatus of Embodiments 3 to 6also provides an advantage in the projection lens 4. Specifically, whenthe polarization splitting direction or the wavelength splittingdirection is set to the long side direction of the liquid crystalmodulation panel, it is possible to set the horizontal direction withnarrow illumination angle distribution shown in FIG. 10(A) to thedirection in which the projection lens 4 has a large projection fieldangle. This can reduce the width of a luminous flux transmitted in adirection in which an aperture eclipse of the projection lens 4 calledvignetting occurs. In other words, the advantage produces the effect ofreducing vignetting due to the pupil aperture eclipse of the projectionlens 4 to prevent a reduction in light amount at the edge of an imagearea projected on the light diffusion screen 5, thereby producing aprojected image of uniform light intensity distribution.

[0203] It should be noted that, while Embodiments 4 to 6 descried aboveemploy the reflection type screen to form the image display system, thescreen may be of the reflection type or a transmission type.Specifically, when a screen with predetermined diffusion is used, aprojection type image display apparatus can function to allow a user todirectly view the screen 5 to recognize an image.

[0204] As described above, according to Embodiments 1 to 6, it ispossible to realize an illumination optical system which can use lightfrom a light source with high efficiency and provide an illuminationluminous flux with high uniform illuminance.

[0205] The illumination optical system can be used as an illuminationsection of a projection display optical system to realize a projectiondisplay optical system and a projection type image display apparatuswhich can provide a projected image with a higher brightness and a highcontrast.

[0206] While preferred embodiments have been described, it is to beunderstood that modification and variation of the present invention maybe made without departing from scope of the following claims.

What is claimed is:
 1. An illumination optical system which illuminatesan illumination surface with a generally telecentric illuminationluminous flux, comprising: at least one optical element, wherein lightintensity distribution of the illumination luminous flux on theillumination surface changes depending on a deviation angle of anincident ray with respect to a normal to the illumination surface,wherein the optical element optically operates the illumination luminousflux such that a ratio of angle widths at which light intensity reacheshalf of a peak value in each of two axis directions orthogonal to eachother on the illumination surface is an aspect ratio of 2:1 or higher.2. The illumination optical system according to claim 1, wherein anangle width at which light intensity reaches half of a peak value in afirst axis direction on the illumination surface is twice or more anangle width at which the light intensity reaches half of a peak value ina second axis direction orthogonal to the first axis direction.
 3. Anillumination optical system which optically operates an illuminationluminous flux incident as a generally collimated luminous flux,comprising: an optical integrator which performs splitting andrecombination on the illumination luminous flux in a first axisdirection on a section generally orthogonal to a traveling direction ofthe illumination luminous flux; and a light intensity conversion elementwhich performs conversion of light intensity distribution of theillumination luminous flux in a second axis direction orthogonal to thefirst axis direction on the section.
 4. The illumination optical systemaccording to claim 3, wherein the illumination luminous flux has afinite outside shape and has generally Gaussian profile intensitydistribution.
 5. The illumination optical system according to claim 3,wherein the illumination optical system produces a luminous flux whichhas a generally rectangular outside shape on a section generallyorthogonal to a traveling direction of the illumination luminous fluxand produces generally uniform light intensity distribution in the areaof the generally rectangular shape.
 6. The illumination optical systemaccording to claim 3, wherein the illumination optical system produces aluminous flux which has a generally rectangular outside shape on asection generally orthogonal to a traveling direction of theillumination luminous flux, and the light intensity conversion elementprovides a smooth change for light intensity distribution in the area ofthe generally rectangular shape.
 7. The illumination optical systemaccording to claim 6, wherein the light intensity distribution providedby the light intensity conversion element includes a higher lightintensity toward an edge from the center of the area of the generallyrectangular shape.
 8. The illumination optical system according to claim7, wherein the distribution including a higher light intensity toward anedge from the center of the area of the generally rectangular shape isprovided for correcting a reduction in light transfer efficiency due toan aperture eclipse of a projection lens which projects a luminous fluxemerging from the illumination optical system onto a projection surface.9. The illumination optical system according to claim 3, furthercomprising a polarization conversion element which converts a luminousflux into linearly polarized light having a predetermined polarizationdirection in an optical path in a direction of integration by theoptical integrator.
 10. The illumination optical system according toclaim 3, wherein the light intensity conversion element performs ashuffling operation on part of an incident luminous flux to reverse acentral portion and a peripheral portion thereof.
 11. The illuminationoptical system according to claim 3, wherein the light intensityconversion element is an afocal optical system which provides distortionaberration for a pupil in a predetermined one-dimensional direction ofan incident luminous flux.
 12. A projection display optical systemcomprising: the illumination optical system according to claim 1; aspatial light modulation element which modulates a luminous fluxemerging from the illumination optical system by a group of pixelsarranged two-dimensionally; and a projection lens which projects theluminous flux modulated by the spatial light modulation element onto aprojection surface.
 13. The projection display optical system accordingto claim 12, wherein the spatial light modulation element is one of amicromirror array device, a reflection type liquid crystal modulationelement, and a transmission type liquid crystal modulation element. 14.The projection display optical system according to claim 12, wherein thespatial light modulation element is a reflection type liquid crystalmodulation element, and the projection display optical system furthercomprising at least one polarization beam splitting element disposed inan optical path from the illumination optical system to the reflectiontype liquid crystal modulation element, wherein a directionperpendicular to a direction in a splitting surface of the polarizationbeam splitting element matches a direction in which an angle width atwhich light intensity reaches half of a peak value in the lightintensity distribution is larger, of two axis directions orthogonal toeach other on the illumination surface.
 15. The projection displayoptical system according to claim 12, wherein the spatial lightmodulation element is a reflection type liquid crystal modulationelement, and the projection display optical system further comprising atleast one wavelength selective deviating element disposed in an opticalpath from the illumination optical system to the reflection type liquidcrystal modulation element, wherein a direction perpendicular to adirection in a deviating surface of the wavelength selective deviatingelement matches a direction in which an angle width at which lightintensity reaches half of a peak value in the light intensitydistribution is larger, of two axis directions orthogonal to each otheron the illumination surface.
 16. The projection display optical systemaccording to claim 12, further comprising a plurality of transmissiontype liquid crystal modulation elements as the spatial light modulationelement, and one of a wavelength selective deviating element and adeflecting direction selective deviating element which combines luminousfluxes modulated by the respective transmission type liquid crystalmodulation elements and is disposed in an optical path from theplurality of transmission type liquid crystal modulation elements to theprojection lens, wherein a direction perpendicular to a direction in adeviating surface by the deviating element matches a direction in whichan angle width at which light intensity reaches half of a peak value inthe light intensity distribution is larger, of two axis directionsorthogonal to each other on the illumination surface.
 17. A projectiondisplay optical system comprising: the illumination optical systemaccording to claim 3; a spatial light modulation element which modulatesa luminous flux emerging from the illumination optical system by a groupof pixels arranged two-dimensionally; and a projection lens whichprojects the luminous flux modulated by the spatial light modulationelement onto a projection surface.
 18. The projection display opticalsystem according to claim 17, wherein the spatial light modulationelement is one of a micromirror array device, a reflection type liquidcrystal modulation element, and a transmission type liquid crystalmodulation element.
 19. The projection display optical system accordingto claim 17, wherein the spatial light modulation element is areflection type liquid crystal modulation element, and the projectiondisplay optical system further comprising at least one polarization beamsplitting element disposed in an optical path from the illuminationoptical system to the reflection type liquid crystal modulation element,wherein a direction perpendicular to a direction in a splitting surfaceof the polarization beam splitting element matches a direction in whichthe optical integrator performs the splitting and recombination.
 20. Theprojection display optical system according to claim 17, wherein thespatial light modulation element is a reflection type liquid crystalmodulation element, and the projection display optical system furthercomprising at least one wavelength selective deviating element disposedin an optical path from the illumination optical system to thereflection type liquid crystal modulation element, wherein a directionperpendicular to a direction in a deviating surface of the wavelengthselective deviating element matches a direction in which the opticalintegrator performs the splitting and recombination.
 21. The projectiondisplay optical system according to claim 17, further comprising aplurality of transmission type liquid crystal modulation elements as thespatial light modulation element, and one of a wavelength selectivedeviating element and a deflecting direction selective deviating elementwhich combine luminous fluxes modulated by the respective transmissiontype liquid crystal modulation elements and is disposed in an opticalpath from the plurality of transmission type liquid crystal modulationelements to the projection lens, wherein a direction perpendicular to adirection in a deviating surface of the deviating element matches adirection in which the optical integrator performs the splitting andrecombination.
 22. A projection type image display apparatus comprising:a light source which emits an illumination luminous flux; and theprojection display optical system according to claim
 12. 23. An imagedisplay system comprising: the projection type image display apparatusaccording to claim 22; and a screen which forms the projection surface,wherein the screen allows observation of a projected image with one ofdivergent reflection light and divergent transmission light havingpredetermined directivity.
 24. A projection type image display apparatuscomprising: a light source which emits an illumination luminous flux;and the projection display optical system according to claim
 17. 25. Animage display system comprising: the projection type image displayapparatus according to claim 24; and a screen which forms the projectionsurface, wherein the screen allows observation of a projected image withone of divergent reflection light and divergent transmission lighthaving predetermined directivity.